When pairing the Elite Direto with Garmin Edge 520 what gear ratio should I enter on the Edge 520 sensor settings screen? The default shows 2.73. I have a 34/50 chainring and a Shimano Ultegra 11/32 cassette.

The gear ratio is a specific Garmin parameter that should be linked to gear itself. It isn't related to the trainer.I suggest you to contact Garmin to ask for details. Or maybe some other Garmin user here can give you some information. Let's see